void polgrid (rmax, rmin, mode, larray, dim, ntheta, color) POLPLT.C Level 2
float rmax The maximum radius of grid.
float rmin The minimum radius of grid.
int mode = 0 for log or db.
= 1 for linear plots.
char *larray[ ] An array of string labels.
int dim The number of labels (the origin and rmax are not labeled).
int ntheta The number of radial spokes. Must be an even number.
int color The color of the labels.
polgrid() draws a polar grid. rmax and rmin are the maximum and minimum values of the radial coordinate. If mode is 0, the values of rmax and rmin are those of the outer- and innermost circular grid lines expressed in user units [e.g., -20. for -20 db or -1.5 for 10 exp(-1.5)]. Otherwise rmin should be set to 0.0. larray is an array of string 
labels of size dim. The outermost circle and the origin are not labeled. Therefore, there are dim+1 circles. col sets the color for labels. Alternate radial lines go to the origin; therefore, ntheta should be an even number.